Clothes washing machine with an improved roller drive mechanism



K. O. SISSON Jan. 19, 1965 CLOTHES WASHING MACHINE WITH AN IMPROVED ROLLER DRIVE MECHANISM 3 SheetsSheet 1 Filed Aug. 20, 1963 Hanna): 0. $3302? H28 ATTORNEY K. O. SISSON Jan. 19, 1965 3 Sheets-Sheet 2 Filed Aug. 20, 1963 n mm M NQ m5 M0 fi M m M W R 2%: \i i &

H15 ATTORNEY Jan. 19, 1965 K. o. SISSON 3,165,911

CLOTHES WASHING MACHINE WITH AN IMPROVED ROLLER DRIVE MECHANISM Filed Aug. 20, 1963 5 Sheets-Sheet 5 INVENTOR Kennel): 0. 521950)? H16 ATTORNEY United States Patent 3,165,911 CLOTHES WASIWG MACHlNE WlTl-l AN 1M- PRGVED RGLLER DRIVE MECHANESM Kenneth O. Sisson, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Aug. 20, 1963, Ser. No. $593,386 6 Claims. ((31. 68-23) This invention relates to a domestic appliance and more particularly to an improved roller drive mechanism for agitating and spinning in a clothes washer.

Roller drive mechanisms, such as taught in the patent to Brucken 3,037,321, issued April 30, 1963, use certain self-energizing rollers as idler members between the motor and the driven member for producing either agitate or spin. Each of these rollers is provided with a resilient tire portion of polyurethane or the like as the motion transmitting surface. During the life of the roller, the tire portion may wear unevenly in a manner to form an undulated or washboard-like surface thereon. When this wear phenomenon occurs, a smooth driving connection is lacking between the drive motor and the driven member and the mechanism becomes noisy due to the added vibration in the system.

In clothes washers using vertical reciprocation, it is desirable to have an agitator which moves uniformly, i.e., a vertically reciprocable agitator which has a constant rate acceleration and deceleration as it moves from its low point through the mid-stroke to the top of its travel and then downwardly through the mid-stroke to the bottom of its travel. Jerky agitator action results in uneven clothes washing and added strain on the structural members of the drive mechanism. When the acceleration and deceleration is smooth, clothes washing results are better and the stresses on the bearings are minimized.

In prior art belt driven mechanisms, such as taught in my Patent 3,006,216 issued October 31, 1961, the motor serves as the flywheel to stabilize the movements of the agitator. But the roller drive mechanism consists of two decoupled systems of motion--the rotating prime mover system including the motor rotor and its powershaft and the vertically reciprocable agitator system including the agitate shaft and its associated motion translating components for changing rotary motion to reciprocating motion. A self-energizing roller connects the two systems. Since the reciprocating inertia of the agitating system is greater than the rotating inertia of the prime mover system, the agitator will tend to run away from its drive roller. For instance, on the second half of its up stroke, the agitator will tend to continue upwardly in a manner to move away from its driven relationship with its drive roller; and, on the second half of the down stroke, the agitator, due to its weight, will tend to drop away from its driven relationship with the drive roller. Such an inconsistent driving connection between motor and agitator is accentuated by rollers having an irregular driving surface and, over a period of time, the agitator is caused to operate at inconsistent speeds. For instance, an agitator, without this invention and designed to operate at 330 strokes per minute, was found to reciprocate at 360 strokes per minute on normal load and at 390 strokes per minute on no load.

Accordingly, it is an object of this invention to provide in a roller drive mechanism means for compensating for irregularities on the surface of roller tires, thereby to provide for constant rate acceleration and decleration of a vertical clothes washer agitator.

A further object of this invention is the provision of a driven drum in a roller drive mechanism having an inertia device sufiiciently weighted to compensate for irregular drive or idler roller wear.

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Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a schematic sectional view, partly in elevation, of a clothes washer provided with the improved roller drive agitate and spin mechanism of this invention;

FIGURE 2 is a sectional view of the improved roller drive agitate and spin mechanism, partly in elevation, showing the improved driven agitate and spin drums of this invention;

FlGURES 3 and 4 are bottom and top elevational views, respectively, of the agitate drum portion of the agitate drum assembly;

FIGURE 5 is a fragmentary perspective view of the improved roller drive mechanism of this invention;

FIGURE 6 is a fragmentary sectional view of the spin roller; and

FIGURES 7 and 8 are bottom and top elevational views, respectively, of the inertia device portion of the agitate drum assembly.

For use with this invention and with reference to FIGURE 1, a clothes washer 2% is comprised of a control housing assembly 22 and a casing 24. The casing 24 is generally divided into a mechanism portion or compartment as and a washing compartment or water container chamber 28. A generally centrally located bulkhead 3t) separates the mechanism compartment 26 from the water container chamber 28 which is further bounded by a cylindrical water container wall 32. Within the water container 32 is a spin tub 34 having a top opening 36 and a plurality of centrifuging outflow ports 38. The ports 38 are designed to permit the egress of water from the tub 34 when the tub is rotated at high speed. For filling the tub 34 with water a conventional water supply system may be provided with a hot water solenoid actuated valve and a cold water solenoid operated valve 42 which are manifolded into a mixed water supply conduit 44 terminating at a chute overlying the opening 36 of the tub. Within the tub 3 an agitator or pulsator 43 is adapted to reciprocate vertically to circulate or agitate the water admitted through the water supply conduit 44. Thus, clothing placed within the tub 34 is washed as the agitating action of the pulsator 48 forces surging toroidal currents of washing fluid and detergent through the fabric. Conventional sequential operating timer means, shown generally at 56) on the control housing 22, may be included selectively to admit water through the supply conduit 44-, to spin the tub 34 and to vertically reciprocate the agitator or pulsator 48.

Prior art roller drive mechanisms for selectively spinning tub 34 and reciprocating an agitator 4% are taught in the aforementioned Brucken patent, in my Patent 3,- 060,712 issued October 30, 1962, and in my copending application Serial No. 128,074 filed July 31, 1961. This invention is directed to an inertia device for use in combination with these roller drive mechanisms, one of which is shown generally at 51 in FIGURE 1, said device pro viding for constant rate vertical agitation and serving to overcome the adverse effects of irregular wear on roller surfaces.

The roller drive mechanism 51 is suspended from a stationary shaft enclosing housing portion 54 which is connected to a resilient cup-shaped support member 56. The support member 5a, in turn, is ailixed to an opening 53 in the bulkhead Bail-a suitable sealing gasket being provided to effect a water-tight connection therebetween. Extending upwardly from the stationary enclosing housing 54 is an agitate or pulsate shaft 62 to which the agitator 48 3 is connected and a spin shaft 64 which is connected as by a tub support nut to the bottom wall of the spin tub 34-. In order to dampen'excessive gyrating or swinging movement of the agitate and spin mechanisms lower end, a snubber device may be used. For additional details pertaining to the general operation of the roller drive type mechanism, reference may be had to the aforementioned Bruclten patent. In accordance with this invention note that the shaft enclosing housing 5 is connected to a motor end frame extension and support means 86 which serves to carry a reversible drive motor or prime mover 32 thereabove and includes studs or bosses such as 84 for rotatabiy carrying therebelow an agitate drum assembly 86 and agitate arm assembly 33 which cooperate to reciprocate vertically the agitate shaft 62.

Carried at the bottom of the spin shaft 64 is a spin drive assembly ltltl (FIGURE 2). The spin drive assembly 1&0 is comprised of a spin drum or roller wheel 162, a spin brake subassembly 184 in an upper cavity of the spin drum and an impact safety clutch subassembly 136 in a lower cavity of the spin drum. The spin drum 1G2, driven by a spin drive idler roller 103, is connected to the spin shaft 64- through a spin drum brake cam or bushing 198 and a spin roll stop as detailed more particularly in my copending application Serial No. 128,074 which is assigned to the same assignee as this invention.

In brief, and while the spin tub is coasting to a stop,.

the brake cam 13% rotates relatively to the spin roll stop 11% and, in so doing, is shift-ably cammed axially thereto to apply the spin tub brake. To effect a spin driving connection between the motor and the spin tub, the brake cam 108 rotates in the opposite direction relatively to the spin roll stop 110 until the respective camming ramps or teeth such as 1%9 lock in a solid driving connection.

The spin brake subassembly 1214 is of the disc type which consists of a brake plate 112 mounted on the motor lower end frame or support 86 the brake lining 114- keyed against relative rotation to the spin drum and springs 116 and 118 which are assembled inside the cavity at the top of the spin drum. Two types of springs are used in the brake subassembly. Two spring washers 116 are used to control the loading between the brake lining 114 and the brake plate 112 during the braking period. In addition to the springs 116, three, two-pound coil brake teaser springs 118 are circumferentially arranged about the spin drum 162 and are used to apply a combined constant load of six pounds between the brake lining 114 and the brake plate 112 as the means for rapidly applying full braking force at the conclusion of spin.

The impact safety clutch subassembly 106 is mounted inside the bottom of the spin drum 1132 and is comprised of a clutch plate 120 sandwiched between two clutch linings 122, 124. The clutch plate 120 is keyed to the top of the spin brake cam MS as at 123 and the clutch linings are keyed to the spin drum by means of undulating or sine wave peripheral edges 125.

Pressure is applied to the clutch linings 122, 124 by means of a spring washer 126 which is separated from the clutch lining 124 by a fiat washer 127 and held in place by an annular combination inertia and retainer device 128 mounted on the bottom of the spin drum 192. The pressure load on the clutch linings 122, 12-; is set by adjusting several screws 130 that mount the retainer on the bottom of the spin drum at a specified torque. This pressure is set so the clutch does not slip under normal operating conditions. However, the clutch can slip to limit the torque the spin drum brake cam 108 transmits to the spin roll stop 111 and this safety connection thereby eliminates the possibility of severe impact loads on the spin drum brake cam 108. For example, slipping action of the clutch 1% can occur when the electrical circuit to the washer motor 82 is opened by the lid switch (actuated by the opening and closing of the clothes Washer access lid) during a spin period and 1. then reclosed before the spin tub 34 comes to a com plete stop.

The agitate drum assembly 85 consists of a die cast aluminum roller wheel or drum 134 (FIGURES 3 and 4) with a shaft and bearing assembly 136 pressed into its upper hub 133. The split lower hub 1 10 of the agitate drum forms an inclined socket for the shaft 14-2 of the agitate arm assembly 88 tightening of a bolt 1433 serving to lock the shaft 142 in place. A cast iron ring 14-4- (FIGURES 2 and 7) is mounted on the top of the agitate drum and includes recesses 145 to receive ribs 147 on the drum for positioning one with respect to the other. Bolts 14% extending through openings 151 into tapped. ports 153 hold the parts together. This ring adds Sll'i'llfllfilli weight to the agitate drum assembly to assure a constant rate of acceleration and deceleration for the agitator and to compensate for irregular surface wear on the tire of roller 148. To locate the agitate drum assembly, the shaft portion of the bearing assembly 136 is mounted into the boss 84 of the motor lower end frame or support 8%) and a bolt 83 tightened.

The agitate arm assembly 88 consists of a die cast aluminum arm 156 with a shaft and bearing assembly 152 pressed into one end. The shaft 142 thereof is mounted into the inclined hub of the agitate drum. The opposite end of the agitate arm 15% is connected to the agitate shaft $23 by means of a flexible rubber mount This mount screws into a spherical bearing which is mounted in a socket in the end of the agitate arm 15d. Additional details relative to the flexible mount are set forth in my aforementioned patent 3,060,712.

The stack up of the spin drive assembly is as follows. A spin drum bushing 166 is press fit from the bottom into the top collar 162 of the spin drum, said bushing having a lower annular flange 164 for axially loosely retaining the spin brake cam 1% and the impact clutch assembly 166 in the lower cavity of the spin drum. The brake assembly 1&4 is seated within the upper cavity of the spin drum just covering the teaser springs 118. Then the spin drive assembly is slipped over the lower end of the cylindrical spin shaft 64 and the spin roll stop 110 slipped over the exposed depending end of the spin shaft, a spline 111 preventing relative rotation of the spin roll stop relative to the spin shaft 64. A nut on the spin shaft retains the entire stack up on the spin shaft.

Next, the flexible connector 154 can be threadedly engaged with the tapped end of the agitate shaft 62 and the entire assembly connected to the spherical bearing 156 of the agitate arm assembly 83 as taught more fully in my patent 3,G60,712.

Turning now to FIGURE 5, the agitate roller 148 and the spin roller 103 are shown on the improved roller drive mechanism. Each roller assembly is the same. Taking the spin roller 103 as representative and referring to FIGURE 6, the roller is formed with a polyurethane tire 17d molded onto an aluminum die cast insert 172. A sintered bronze bushing 173 is pressed into the insert to form a hub for the roller. A peripherally grooved nylon tension spring adapter 174 is assembled on each end of the insert and the entire roller assembly is mounted on a spool-like spacer 176 which is fastened as by a screw 17% screwed into the motor lower end frame or support Kit. The diameter of the center shaft of the spool 176 through the roller is smaller than the diameter of the center hole 181 through the tension spring adapter. Therefore a rather sloppy fit is effected for each roller so that each roller 103, 14-8 is free to float about relative to its respective drum 102 or 134 in all directions from the center of the roller. Spin roller 103 is spring biased by springs 131 (FIGURE 6) and 182 toward the spin drum 1&2 and the powershaft portion 188; and agitate roller 148 is spring biased by springs 132 and 134 toward the agitate drum 134 and the powershaft portion 19ll-common spring 182, at opposite ends thereof, providing a radially inward bias to both rollers. Each roller can then be drawninto a solid driving connection between the motor powershaft 186 and its respective drum depending upon the direction of motor operation roller 103 wedging between spin drum 102 and powershaft portion 138 when the motor operates in one direction and roller 148 wedging between agitate drum portion 134 and powershaft portion 19% when the motor operates in a reverse direction. This floating action of the roller is very essential in the overall operation of the mechanism and is defined as the self-energizing characteristic of the rollers in the patent to Brucken 3,087,321 to which reference may be had for further details in this regard. Sufiice it at this point to recognize the free-floating characteristic of the polyurethane tired roller gives rise to a scuffing action on the tire surface of the roller which is not in power transmitting relationship. This scuffing occasionally creates an undulated surface on the roller tire which causes inconsistent transmission of drive forces between the roller and its respective drum when the roller is in power transmitting relationship.

This invention is directed to controlling the operation of the roller drive mechanism by minimizing the irregularities on the surfaces through the use of inertia menibers. In the spin system the inertial member is provided in the form of the retainer 128 which is given suflicient mass to overcome the bumpy surface of the spin roller, thereby to provide a smooth consistent driven characteristic in the spin drum 102. In the agitate system the inertia member is provided in the form of the cast iron ring 144 which provides for constant rate acceleration and deceleration in the agitator.

It should now be seen that an improved roller drive mechanism has been provided which overcomes-problems arising with a decoupled driving arrangement in a manner to effect a relatively quiet, smoothly operating agitating and spinning mechanism for producing improved washing results with less structural stress.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In combination, a washing machine having a tub, an agitator in said tub, and a roller drive mechanism for reciprocating said agitator and rotating said tub, said mechanism comprising (a) a support means,

(b) areversible motor,

(c) an agitate shaft supporting said agitator on an upper end thereof,

(d) a rotatable spin shaft drivably connected to said tub,

(e) a shaft housing aflixed to carry said support means and at least partially enclosing said agitate shaft and said spin shaft,

(f) an agitate drum assembly rotatably supported by said support means and having an agitate drum and a first inertia device,

(g) said agitate drum having an angularly directed crank portion,

(h) an agitate arm assembly having a rocking end universally movably connected to said agitate shaft and a crank end relatively rotatably connected to said crank portion,

(i) a spin drive assembly drivably connected to said spin shaft and coaxial therewith and including a spin drum and a second inertia device,

(j) powershaft means drivably connected to said motor and having a powershaft agitate portion adjacent said agitate drum and a powershaft spin portion adjacent said spin drum, and

(k) an agitate roller and a spin roller rotatably and spring-biasingly, relatively laterally movably sup ported by said support means adjacent said powershaft agitate portion and said powershaft spin portion respectively for self-energizingly positioning themselves in power transmitting relationship between the respective powershaft agitate or spin portions and the respective agitate or spin drums in accordance with the direction of motor operation,

(I) one of said agitate or spin rollers being in springbiased, lightly scufling, non-driving engagement with its respective agitate or spin drum when the other of said agitate or spin rollers is in power transmitting relationship with its respective agitate or spin drum,

(m) each of said agitate and spin rollers having a resilient polyurethane tire thereon subjected to irregular wear at the surface thereof by the scuffing engagernent of the roller tire with its respective agitate or spin drum,

(:2) said first inertia device including an annular mass coaxial with said agitate drum and fastened thereto and having sufiicient weight to overcome the effects of said irregular tire wear on the transmission of power from said agitate roller to said agitate drum thereby to provide smooth acceleration and deceleration of said'agitator when said motor is operating in one direction, N

(0) said second inertia device including an annular mass coaxial with said spin drum and fastened thereto and having suflicient weight to overcome the effects of said irregular tire wear on the transmission of power from said spin roller to said spin drum thereby to provide smooth acceleration of said spin tub when said motor'is operating in another direction. I

2. In combination, a washing machine having a tub,

an agitator in said tub, and a roller drive mechanism for reciprocating said agitator and rotating said tub, said mechanism comprising (a) asupport means,-

(b) areversible motor,

(c) an agitate shaft supporting said agitator on an upper end thereof,

(d) a rotatable spin shaft drivably connected to said tub,

(e) an agitate drum assembly rotatably supported by said support means and having an agitate drum and 'a first inertia device,-

(f) said agitate drum having an angularly directed crank portion,

(g) an agitate arm assembly having a rocking end universally movably connected to said agitate shaft and a crank end relatively rotatably connected to said crank portion,

(h) a spin drive assembly drivably connected to said spin shaft and including a spin drum and a second inertia device, 1

(i) powershaft means drivably connected to said motor. and having a powershaft agitate portion adjacent,

said agitate drum and a powershaft spin portion adjacent said spin drum, and (j) an agitate roller'and a spin roller rotatably relatively laterally movably supported by said support means adjacent to and biasingly toward said powershaft agitate portion and said powershaft spin portion respectively for self-energizingly positioning themselves in power transmitting relationship between the respective powershaft agitate or spin portions and the respective agitate or spin drums in accordance with the direction of motor operation,

(k) one of said agitate orspin rollers being in lightly scufling, non-driving engagement with its respectiveagitate or spin druin when the other of said agitate or spin rollers is in power transmitting relationship with its respective agitate or spin drum,

(I) each of said agitate and spin rollers having a resilient tire'thereon subjected to irregular wear at the surface thereof by the scufling engagement of the roller tire with its respective agitate or spin drum,

(In) said first inertia device being fastened for movement with said agitate drum and having sufficient weight to overcome the effects of said irregular tire wear on the transmission of power from said agitate roller to said agitate drum thereby to provide smooth acceleration and deceleration of said agitator when said motor is operating in one direction,

(11) said second inertia device being fastened for movement with said spin drum and having suiiicient weight to overcome the efiects of said irregular tire wear on the transmission of power from said spin roller to said spin drum thereby to provide smooth acceleration of said spin tub when said motor is operating in another direction.

3. In combination, a washing machine having an agitator, and a roller drive mechanism for moving said agitator, said mechanism comprising a support means, a reversible motor, an agitate shaft, a shaft housing affixed to carry said support means and enclosing said agitate shaft, an agitate drum assembly rotatably supported by said support means and having an agitate drum and an inertia device, said agitate drum having an angularly directed crank portion, an agitate arm assembly having a rocking end universally movably connected to said agitate shaft and a crank end relatively rotatably connected to said crank position, powershaft means drivably connected to said motor and having a powershaft portion adjacent said agitate drum, an agitate roller rotatably and spring biasingly, relatively laterally movably supported by said support means adjacent said powershaft portion for selfenergizingly positioning itself in power transmitting relationship between said powershaft portion and said agitate drum when said motor is operating in one direction and in spring-biased, lightly scufling, non-driving engagement with said agitate drum when the motor is operating in the reverse direction, said agitate roller having a resilient tire thereon subjected to irregular wear at the surface thereof when said motor is operating in said reverse direction by the scuffing engagement with said tire with said agitate drum, said inertia device including an annular mass coaxial with said agitate drum and fastened thereto and having sufiicient weight to overcome the effects of said irregular tire wear on the transmission of power from said agitate roller to said agitate drum thereby to provide smooth acceleration and deceleration of said agitator when said motor is operating in said one direction.

4. In combination, a washing machine having an agitator, and a roller drive mechanism for moving said agitator, said mechanism comprising a support means, a reversible motor, an agitate shaft, an agitate drum assembly rotatably supported by said support means and having an agitate drum and an inertia device, said agitate drum having a crank portion, an agitate armassembly having a rocking end universally movably connected to said agitate shaft and a crank end relatively rotatably connected to said crank portion, powershaft means drivably connected to said motor and having a powershaft portion adjacent said agitate drum, an agitate roller rotatably, relatively laterally movably supported by said support means adjacent to and biasingly toward said powershaft port-ion for self-energizingly positioning itself in power transmitting relationship between said powershaft portion and said agitate drum when said motor is operating in one direction and in lightly scufling, non-driving engagement with said agitate drum when the motor is operating in the reverse direction, said agitate roller having a resilient tire thereon subjected to irregular wear at the surface thereof when said motor is operating in said reverse direction by the sending engagement with said tire with said agitate drum, said inertia device being fastened for movement with said agitate drum and having suflicient weight to overcome the efiects of said irregular tire wear on the transmission of power from said agitate roller to said agitate drum thereby to provide smooth acceleration and deceleration of said agitator when said motor is operating in said one direction.

5. In a washing machine, a tub, means for agitating in said tub, means for rotatably supporting said tub, a motor, power transmitting means drivingly connecting said motor to said tub and said agitating means for rotating said tub and for moving said agitating means, said power transmitting means comprising a plurality of self-energizing motion transmitting rollers having diiferent moment arms, and means for selectively transmitting motion through different combinations of rollers to select predetermined diiferent speed ratios between said motor and said tub and said agitating means, at least one of said roilers scuffing the surface of another of said rollers when they are not in the combination of rollers being used to transmit motion, said at least one of said rollers having a polyurethane tread subjected to irregular wear by said scutling, and inertia means on said another of said rollers and rotatable therewith and having sufiicient weight to overcome the inconsistent motion transmitting effects of said irregular wear on the transmission of power from said at least one of said rollers to said another of said rollers.

6. In a washing machine, a tub, means for agitating in said tub, a motor, power transmitting means drivingly connecting said motor to said agitating means for moving said agitating means, said power transmitting means comprising a plurality of self-energizing motion transmitting rollers having different moment arms, and means for selectively transmitting motion through a combination of rollers to select a predetermnied speed ratio between said motor and said agitating means, at least one of said rollers scuffing the surface of another of said rollers when they are not in the combination of rollers being used to transmit motion, said at least one of said rollers having a resilient tire subjected to irregular wear by said scuffing, and inertia means on said another of said rollers and rotatable therewith and having suificient weight to overcome the inconsistent motion transmitting effects of said irregular wear on the transmission of power from said at least one of said rollers to said another of said rollers thereby to provide smooth acceleration and deceleration of said agitating means.

References Cited by the Examiner UNITED STATES PATENTS 3,060,712 10/62 Sisson 6823 3,087,321 4/63 Brucken 68-23 3,091,956 6/63 Brucken et al. 6823 WALTER A. SCHEEL, Primary Examiner. 

6. IN A WASHING MACHINE, A TUB, MEANS FOR AGITATING IN SAID TUB, A MOTOR, POWER TRANSMITTING MEANS DRIVINGLY CONNECTING SAID MOTOR TO SAID AGITATING MEANS FOR MOVING SAID AGITATING MEANS, SAID POWER TRANSMITTING MEANS COMPRISING A PLURALITY OF SELF-ENERGIZING MOTION TRANSMITTING ROLLERS HAVING DIFFERENT MOTION ARMS, AND MEANS FOR SELECTIVELY TRANSMITTING MOTION THROUGH A COMBINATION OF ROLLERS TO SELECT A PREDETERMINED SPEED RATIO BETWEEN SAID MOTOR AND SAID AGITATING MEANS, AT LEAST ONE OF SAID ROLLERS SCUFFING THE SURFACE OF ANOTHER OF SAID ROLLERS WHEN THEY ARE NOT IN THE COMBINATION OF ROLLERS BEING USED TO TRANSMIT MOTION, SAID AT LEAST ONE OF SAID ROLLERS HAVING A RESILIENT TIRE SUBJECTED TO IRREGULAR WEAR BY SAID SCUFFING, AND INERTIAL MEANS ON SAID ANOTHER OF SAID ROLLERS AND ROTATABLE THEREWITH AND HAVING SUFFICIENT WEIGHT TO OVERCOME THE INCONSISTENT MOTION TRANSMITTING EFFECTS OF SAID IRREGULAR WEAR ON THE TRANSMISSION OF POWER FROM SAID AT LEAST ONE OF SAID ROLLERS TO SAID ANOTHER OF SAID ROLLERS 